阅读说明：本技术 溅射靶和溅射靶的制造方法 (Sputtering target and method for producing sputtering target ) 是由 杉本圭次郎 村田周平 于 2019-03-12 设计创作，主要内容包括：本发明提供一种钼的含量为99.99质量％以上、相对密度为98％以上、平均晶粒尺寸为400μm以下的溅射靶。(The present invention provides a sputtering target having a molybdenum content of 99.99 mass% or more, a relative density of 98% or more, and an average grain size of 400 [ mu ] m or less.)

1. A sputtering target, wherein,

the content of molybdenum is 99.99 mass% or more, the relative density is 98% or more, and the average crystal grain size is 400 μm or less.

2. The sputtering target according to claim 1,

the radiation dose is 0.03cph/cm²The following.

3. The sputtering target according to claim 2,

the radiation dose is 0.02cph/cm²The following.

4. A sputtering target according to any one of claims 1 to 3,

the content of molybdenum is 99.999 mass% or more.

5. The sputtering target according to any one of claims 1 to 4,

the relative density is more than 99%.

6. The sputtering target according to any one of claims 1 to 5,

the average grain size is 200 μm or less.

7. A method for producing a sputtering target according to any one of claims 1 to 6, comprising:

preparing molybdenum powder;

a step of applying a load to the molybdenum powder at a temperature of 1350 to 1500 ℃ to perform hot pressing; and

and hot isostatic pressing the molded body obtained by the hot pressing at a temperature of 1300 ℃ to 1850 ℃.

8. The sputtering target production method according to claim 7,

in the step of performing the hot pressing, a load applied to the molybdenum powder is set to 200kg/cm²～300kg/cm²。

9. The sputtering target production method according to claim 7 or 8,

the hot pressing is carried out for 60 to 300 minutes.

10. The method for producing a sputtering target according to any one of claims 7 to 9,

in the hot isostatic pressing step, the load applied to the molded article is 1300kg/cm²～2000kg/cm²。

11. The method for producing a sputtering target according to any one of claims 7 to 10,

the hot isostatic pressing is carried out for 60 to 300 minutes.

12. The method for producing a sputtering target according to any one of claims 7 to 11,

in the step of preparing the molybdenum powder, a molybdenum powder having a purity of 4N or more and an average particle diameter of 1 to 5 μm is prepared.

Technical Field

The present specification discloses a technique relating to a sputtering target and a method for manufacturing the sputtering target.

Background

In recent years, the ultra-high integration of LSI (large scale integrated circuit) has been advanced, and the use of a material having a lower resistivity as an electrode material or a wiring material has been studied. Under such circumstances, high-purity tungsten has relatively low specific resistance and excellent thermal and chemical stability, and is therefore used as an electrode material or a wiring material.

In the production of electrode materials and wiring materials, a thin film is generally formed by a sputtering method using a sputtering target. Further, as for the electrode material and the wiring material containing high-purity tungsten, a sputtering target made of high-purity and high-density tungsten is desired.

As such a technique, patent documents 1 and 2 propose "a tungsten sintered body sputtering target characterized in that the purity of tungsten is 5N (99.999%) or more and the impurity carbon contained in tungsten is 3wtppm or less". It is considered that "the tungsten sintered body sputtering target" can realize stable reduction of the resistance value in the tungsten film.

Although not relating to the above-described tungsten sputtering target, patent document 3 describes "a method for producing a high-purity molybdenum target for LSI electrodes, which has a purity of 99.999% or more, an alkali metal content of 100ppb or less, and a radioactive element content of 10ppb or less, characterized by dissolving metallic molybdenum or a molybdenum compound to produce a molybdenum-containing aqueous solution, purifying the aqueous solution to crystallize molybdenum-containing crystals, subjecting the crystals to solid-liquid separation, washing and drying, then adjusting high-purity molybdenum powder by thermal reduction, subjecting the high-purity molybdenum powder to pressure molding and sintering, performing electron beam melting to produce a high-purity molybdenum ingot, and then subjecting the ingot to plastic working and mechanical working".

Disclosure of Invention

Problems to be solved by the invention

However, the high-purity tungsten film may not meet the future demand for lower resistance. Therefore, there is a need to find a material that is promising as a substitute for tungsten.

In this regard, the molybdenum film may achieve a sufficiently low resistance value, but the "high-purity molybdenum target for LSI electrodes" described in patent document 3 has the following problems: the yield of particles (particles) during sputtering is high, and the material yield is lowered.

In order to solve the above-described problems, the present specification proposes a sputtering target mainly containing molybdenum and capable of effectively reducing particles generated during sputtering, and a method for manufacturing the sputtering target.

Means for solving the problems

The sputtering target disclosed in the present specification has a molybdenum content of 99.99 mass% or more, a relative density of 98% or more, and an average crystal grain size of 400 μm or less.

Further, a method for manufacturing a sputtering target disclosed in the present specification is a method for manufacturing the sputtering target, and the manufacturing method includes: preparing molybdenum powder; a step of applying a load to the molybdenum powder at a temperature of 1350 to 1500 ℃ to perform hot pressing; and hot isostatic pressing (hot isostatic pressing) the molded body obtained by the hot pressing at a temperature of 1300 ℃ to 1850 ℃.

Effects of the invention

According to the sputtering target and the method for producing the sputtering target described above, the sputtering target mainly contains molybdenum, particles generated during sputtering can be effectively reduced, and such a sputtering target can be efficiently produced.

Detailed Description

Hereinafter, embodiments of the invention disclosed in the present specification will be described.

In the sputtering target according to one embodiment of the present invention, the molybdenum content is 99.99 mass% or more, the relative density is 98% or more, and the average crystal grain size is 400 μm or less. In addition to these constituents, the radiation dose (radiation dose) is preferably 0.03cph/cm²The following.

Conventionally, a sputtering method using a high-purity tungsten sputtering target has been used for an electrode material and a wiring material for manufacturing a high-integration LSI, but a tungsten film formed by the sputtering method may not meet a demand for a lower resistance which is supposed to be further developed in the future.

In contrast, the inventors have studied the film forming characteristics of the high melting point metal, and as a result, have found that a thin film made of molybdenum, which is one of the high melting point metals, can achieve a lower resistance value than a thin film made of tungsten.

Further, as a result of intensive studies on a sputtering target capable of forming a thin film made of molybdenum as described above, the following were found: according to the predetermined sputtering target manufactured by the predetermined manufacturing method, a thin film which can realize a further low resistance value and can be suitably used for semiconductor applications can be formed. With respect to this sputtering target, it is known that: the generation rate of particles during sputtering can be effectively reduced, and the possibility of malfunction of an electronic device comprising a thin film formed therefrom can be reduced.

Hereinafter, such a sputtering target and a method for manufacturing the same will be described in detail.

(composition)

The sputtering target of the present embodiment contains not less than 99.99 mass% of molybdenum and is composed of 4N or more of high-purity molybdenum. If the purity of molybdenum is high, the generation rate of particles is significantly reduced, and on the other hand, if the purity of molybdenum is low, particles tend to increase. Therefore, from the viewpoint of particle reduction, the higher the purity of molybdenum is, the more preferable. From this viewpoint, the content of molybdenum in the sputtering target is preferably 99.999 mass% or more (i.e., 5N or more).

The above purity means a purity in which an inseparable homologous element is removed. That is, the inseparable group-homologous element is tungsten, and the purity is defined as the ratio of the content of molybdenum in the content of an element having a lower detection limit or less and the content of all metal elements other than tungsten. The content of molybdenum was calculated by measurement by Glow Discharge Mass Spectrometry (GDMS).

(relative Density)

In the embodiment of the present invention, the relative density of the sputtering target is 98% or more. The higher the relative density, the more the particles decrease, but if the relative density is low, the particles tend to increase. From this viewpoint, the relative density is preferably 99% or more, and more preferably 99.5% or more.

The relative density of the sputtering target is expressed as relative density (measured density/theoretical density) × 100 (%). Here, the measured density is a density of the sputtering target measured by an archimedes method using pure water as a solvent, and the theoretical density is a theoretical density when the content of molybdenum is 100%.

(grain size)

If the grain size of molybdenum contained in the sputtering target is large, the particles increase, and if the grain size is small, the particles tend to decrease.

Therefore, the average grain size of molybdenum in the sputtering target is 400 μm or less, preferably 200 μm or less. Although there is no problem caused by the excessively small average crystal grain size of molybdenum, the average crystal grain size may be, for example, 15 μm or more, typically 40 μm or more.

The average crystal grain size is calculated as L/N from the number of particles (N.gtoreq.200) present on the straight line and the total length (L) of the straight line by drawing a straight line on the microstructure photograph obtained by observing the surface of the target with an optical microscope until the number of particles N.gtoreq.200. The method for measuring the average crystal grain size is a cutting method defined in JIS G0551.

(radiation dose)

The radiation dose of the sputtering target was set to 0.03cph/cm²The following. When the radiation dose is large, the possibility of malfunction of an electronic device having a molybdenum thin film formed using the sputtering target is increased, and when the radiation dose is small, the possibility of malfunction of such an electronic device is reduced. Therefore, the radiation dose of the sputtering target is preferably 0.02cph/cm²More preferably 0.01cph/cm²The following.

For the above radiation dose, LACS-4000M manufactured by Kyowa Kagaku K.K. was used as a P-10 gas (Ar-CH)₄10%), flow rate of 100 ml/min, measurement time of 99kr, measurement area of 203cm²And the counting efficiency was 80%.

(production method)

As an example of a method for producing the sputtering target described above, the following method can be mentioned: as described below, a powder metallurgy method combining Hot Pressing (HP) and Hot Isostatic Pressing (HIP) is performed on a predetermined molybdenum powder.

First, molybdenum powder was prepared as a raw material. The molybdenum powder preferably has a particle diameter in the range of 0.1 to 10 μm, an average particle diameter of 1 to 5 μm, and a purity of 4N or more. If the particle size of the molybdenum powder is too large, the density may be low. Further, if the particle size is too small, the particle size becomes large, and therefore the handling difficulty increases, and there is a possibility that the productivity is impaired (that is, since the particle size is large, it is difficult to fill a plurality of sheets into a die of a hot press or the like, and the production amount per one time is reduced). When the purity of the molybdenum powder is low, the molybdenum content of the manufactured sputtering target decreases. Therefore, molybdenum powder having a purity of molybdenum of 5N or more is preferably used. In order to reduce the dose of radiation to the sputtering target to be produced, it is also preferable to use 5N or more of molybdenum powder as the raw material.

Next, in the hot pressing step, the molybdenum powder is filled in a predetermined mold such as a mold, and a predetermined load is applied while heating the mold to maintain a predetermined temperature.

Here, as the maximum reaching temperature of the raw material, the load was applied while maintaining the temperature at 1350 ℃ to 1500 ℃. If the temperature at this time is low, the relative density of the sputtering target cannot be sufficiently increased, while if the temperature at this time is high, the particles may be coarse and may increase in size. Therefore, the temperature during hot pressing is 1350 ℃ to 1500 ℃.

The time for maintaining the temperature as described above is preferably 60 to 300 minutes. If the holding time is too short, the density may be low, and if the holding time is too long, the particle size may be coarse.

The magnitude of the load applied at this time is preferably 150kg/cm²～300kg/cm²Particularly, it is more preferable to set the concentration to 200kg/cm²～300kg/cm². In the case where the load is excessively small, the density may be undeniably low. In particular, there is no problem caused by an excessive load. If a mold (dies) or other spare part can withstand, the increase in load is associated with densification. However, it is usually 300kg/cm²The upper limit is on the left and right.

In order to reduce the deviation between the set temperature and the actual temperature during heating in hot pressing, it is preferable to hold the sheet in a temperature range of 800 to 1200 ℃ for 30 minutes, for example, when the sheet is heated.

Thereafter, the molded body obtained in the hot pressing step is subjected to hot isostatic pressing. This makes the manufactured sputtering target higher in density.

In the hot isostatic pressing step, the hot isostatic pressing is performed at a temperature of typically 1300 to 1850 ℃ under the control of 1300kg/cm²～2000kg/cm²The load of (3) is applied for 60 to 300 minutes. If such conditions of temperature, load, and time are not satisfied, there is a problem that the density is low. Therefore, in the hot isostatic pressing, the temperature is more preferably 1400 ℃ to 1850 ℃, and the load is more preferably 1500kg/cm²～1900kg/cm²More preferably, the time is set to 60 minutes to 300 minutes.

The sintered body obtained by hot isostatic pressing may be subjected to shape processing such as grinding as necessary to produce a sputtering target having a predetermined dimensional shape.

The sputtering target thus manufactured has a low generation rate of particles during sputtering and a small dose of radiation, and therefore, the electronic device having the molybdenum thin film formed therefrom has a low possibility of malfunction.

The present invention is not limited to the above-described embodiments, and can be embodied by modifying each component of the embodiments without departing from the scope of the invention. For example, various configurations can be configured by appropriate combinations of a plurality of constituent elements included in the respective embodiments. Further, several components may be deleted from all the components included in the embodiment.